A Catholic cardinal has caused uproar at the Vatican by screening a spurious and anonymous YouTube video that makes alarmist predictions about the growth of Islam in Europe.

The widely debunked seven-minute clip, called "Muslim Demographics" was the talk of an international gathering of bishops on Monday, two days after Cardinal Peter Turkson screened it during a free discussion period.

Turkson, a Ghanaian who is based in the Vatican and is president of its Council for Justice and Peace, sparked consternation among his fellow bishops over the clip.

"As we were arriving this morning I was asked several times, 'Who planned it?, Whose was it?, Who is behind it?", Father Thomas Rosica said at a briefing for journalists, who are not allowed to attend the sessions of the synod, a three-week bishops' conference.

He said the clip had sparked "the most animated" discussion so far at the synod, and one bishop said he would rebut Turkson by presenting a report with contrary data. Pope Benedict did not attend the meeting at which the video screened.

The clip has made Islam top of the agenda at the synod, attended by 262 bishops. "Islam is the buzzword," Rosica said.

Turkson could not be reached for comment on why he chose to screen the video during the Vatican meeting, where the bishops are discussing ways of winning back lapsed Roman Catholics in developed countries. The clip has been viewed over 13 million times on YouTube since it was uploaded by an anonymous user in 2009.

It combines dramatic music with skewed population statistics to make claims about various European countries such as: "In just 39 years France will be an Islamic republic."

Critics have pointed out that the fertility figures used in the video, which claim French women have an average of 1.8 children while French Muslim women have 8.1 children, cannot be genuine as France does not collect statistics by religion.

One bishop present said the Catholic Church should avoid "the trap of behaving like fundamentalist Islam". Another said it was "inappropriate", while a third said the video ran the risk of provoking a "war of religions".

Many prelates from Africa and the Middle East have spoken at the synod about the difficulty of preaching the Gospel in majority Muslim countries and said the situation with Muslims wanting to convert was very sensitive.

According to a study by US-based Pew Research Centre, there were 2.18 billion Christians in 2010, half of them Catholics.

The total number of Muslims of all denominations was 1.6 billion and forecast to increase 35 per cent to 2.2 billion by 2030.

The Holy See's relations with Islam have not always been smooth. In 2006 Pope Benedict gave a speech in Regensburg which was perceived by some Muslims as an attack on Islam.

Asked about his reaction to the cardinal showing the video at the Vatican, Yahya Pallavicini, vice-president of the Islamic Religious Community of Italy, warned against a numbers war based on scare tactics by any side.

Additional reporting by Agence France-Presse

This article appeared in the South China Morning Post print edition as Bishops' fury at Islam video